1. Field of the Invention
The invention relates to a driving force transmission apparatus that switches between an on state in which a rotational force is transmitted between a first shaft and a second shaft and an off state in which no rotational force is transmitted between the first shaft and the second shaft.
2. Description of Related Art
Japanese Patent Application Publication No. 2013-092191 (JP 2013-092191 A) discloses a rotation transmission apparatus including a two-way clutch. In the two-way clutch, rollers of each pair disposed between an inner ring and an outer ring are each retained by a controlling cage and a rotational cage. Energizing a magnet coil provided in the rotation transmission apparatus exerts a force on the controlling cage. This force causes the controlling cage and the rotational cage to rotate relative to each other in a direction in which the circumferential widths of pockets defined between the controlling cage and the rotational cage decrease. Thus, the rollers of each pair are pressed by the controlling retainer and the rotational retainer, moved close to each other, and disengaged from the inner ring and the outer ring. As a result, the two-way clutch enters a disengaged state.
De-energizing the magnet coil allows the controlling cage and the rotational cage to be rotatable. Pressing forces from elastic members cause the controlling cage and the rotational cage to rotate relative to each other in a direction in which the circumferential widths of the pockets increase. Thus, the rollers of each pair come into engagement with the inner ring and the outer ring, so that a torque is transmitted between the inner ring and the outer ring through the rollers.
When the two-way clutch of the rotation transmission apparatus disclosed in JP 2013-092191 A is in an engaged state, the rollers of each pair pressed by the associated elastic member are both in engagement with the inner ring and the outer ring. Suppose that the rotational cage and the controlling cage are rotated relative to each other so as to switch the two-way clutch from the engaged state to the disengaged state. In this case, at least one of the rollers of each pair may fail to disengage from the inner ring or the outer ring. Thus, the two-way clutch may be unable to smoothly change from the engaged state to the disengaged state.